[lexical] Bug Fix: Keep selection inside single-child inline elements

[mayrang]

Description

resolveSelectionPointOnBoundary normalizes selection points at inline element boundaries. For inline elements that return canInsertTextAfter() === false (like LinkNode), it pushes the cursor outside at the right edge. When the inline element contains only a single child, offset 0 is the left edge and offset 1 is the right edge — both get normalized outward, making it impossible to place the cursor inside.

This adds a parent.getChildrenSize() !== 1 guard to the right-edge normalization branch, so single-child inline elements keep the cursor inside at the right edge. Left-edge normalization (which keeps left bias) is unchanged.

Closes #7551

Test plan

• pnpm vitest run --project unit packages/lexical/src/__tests__/unit/LexicalSelection.test.ts — 69 tests pass
  • Single-child link: cursor stays at offset 1 inside the link
  • Multi-child link: cursor normalizes to the next sibling (existing behavior preserved)
• Manual playground:
  • Type "hello", select "hello", insert link, click at end of link text: cursor stays inside the link and further typing extends the link
  • Multi-word link: cursor at end of last child still normalizes outward
• tsc / eslint / prettier clean

[vercel]

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Project	Deployment	Actions	Updated (UTC)
lexical	Ready	Preview	Jul 2, 2026 12:54pm
lexical-playground	Ready	Preview	Jul 2, 2026 12:54pm